Silver halide photographic light-sensitive materials have been handled either in the total darkness or in a safe light having a wavelength region to which the light-sensitive materials are not substantially sensitive, hereinafter simply called a safe light.
Generally, silver halide black-and-white light-sensitive materials and particularly those for industrial use such as those for photomechanical use have mostly been processed in a red safe light from the viewpoints of the characteristics of a light source used and working efficiency.
As have been well known so far in the art, among the light-sensitive materials for industrial use, matte films have been used for duplicating the drawings of machines or structures, maps and so forth, for halftoning aerial photographs by making use of a screen so as to enlarge the photographs or to make them into a composite picture or the like. The so-called `matte film` is a film containing a large amount of matting agent in its layer so as to be opaque. The reason why a film is to be matted by adding a large amount of matting agent in its layer is that a retouch or correction can be made with a pencil or an ink and the retouched or corrected pencil or ink traces can be erased with a rubber eraser, after exposed and processed the film. Thereby, a retouch and write-on may be made on drawings. Accordingly, after exposing and processing such a matte film, it is used for retouching and writing on a drawing by retouching or erasing the traces and for subjecting to a diazo printing and a copying operation.
Generally, these matte films are also mostly handled under s red safe light condition. It is, therefore, usual that these matte films are sensitized to green sensitive regions.
As described above, in the case that an aerial photograph is enlarged upon making it halftoned by making use of a screen or in the like cases, the matte film should desirably have a relatively high sensitivity.
When exposing an image to light emitted from such an ordinary light source as a tungsten or halogen lamp, it is advantageous to make a light-sensitive material have a sensitivity to a relatively longer wavelength side, however, a red safe light is rather easier to handle the light-sensitive material than a green safe light.
In the meantime, there is a technology in which a photo-sensitive wavelength region intrinsic to silver halides can be widened to a long wavelength side by adding a certain kind of dyes into a silver halide emulsion, that is well known in the art as a spectral sensitization technology.
When handling a light-sensitive material in red light condition, usually the light-sensitive material is spectrally sensitized to a wavelength region not longer than 600 nm, that is, to a green region. As for the sensitizing dyes which are applicable to the sensitization to a green region, a variety of cyanine or merocyanine dyes are known.
In general, however, the more the sensitivity of a light-sensitive material is getting higher, the more the light quantity of a safe light is to be small. The working property is deteriorated. This fact may also applied to the case of using a light-sensitive material which is to be handled under red safe light conditions. There is a demand for embodying a light-sensitive material which may be handled under bright red safe light conditions from the viewpoint of working property. It is, however, the state of things that the sensitivity of such a light-sensitive material may not be increased.